The application refers to a device for distance measurement by radar comprising a frequency modulated radar-transmitter and -receiver by which a radar beam is guided onto an object to be measured and which, by mixing of the transmitted frequency with the received frequency, delivers a beat signal; frequency modulating means, by which the transmitted frequency of the radar signal of the doppler signal device is periodically variable in a saw-tooth shaped way and wherein the frequency of the beat signal, due to the travel time of the radar beam reflected by the object, is a measure for the distance of the object, and a signal processing circuit generating a measured value from the beat signal obtained.
Devices of this kind are known. In the radar-transmitter and -receiver mixing takes place of the transmitted and the received signal. The signal received has passed the distance to and from the object, thereby has been transmitted at an earlier instant and thereby has, due to the saw-tooth modulation, a frequency which is a bit different from the frequency of the signal which is emitted at the moment of reception. Thereby a beat frequency occurs. This beat frequency is proportional to the travel time to the object and thereby to the distance from the object to the radar-transmitter and -receiver.